The aims of this study are to produce experimentally various forms of occult filariasis in dog and non-human primates, and to study the elicited immunologic responses in vitro and in vivo. The in vitro study concerns the detection and differentiation of stage and species immunities; the in vivo study involves tracing the fates of the invading parasite and the sequelae to re-exposure, either single or multiple, to the same or a different species of filarial worm, before or after treatment. The filarial parasites being studied include 2 spp. of Brugia (B. malayi and B. pahangi) and 4 spp. of Dirofilaria (D. immitis, D. repens, D. corynodes, D. tenuis and D. magnilarvatum). The undersigned agrees to accept responsibility for the scientific and technical conduct of the project and for provision of required progress reports if a grant is awarded as the result of this application.